Zinc (Zn), a ubiquitous environmental transition metal primarily existing as Zinc ions (Zn2+), plays a critical role in various biological processes. Its extensive application in agriculture, industry, and healthcare has led to significant environmental contamination. However, the mechanistic contribution of Zn2+ to bacterial antibiotic resistance and virulence remains insufficiently understood. This review explores the sources, cycling, and environmental accumulation of Zn2+ in a One Health context, emphasizing their impact on bacterial antibiotic resistance and virulence. Zn2+ promote bacterial antibiotic resistance by regulating efflux pumps, biofilm formation, expression and transfer of antibiotic resistance genes, as well as synergistic effects with other heavy metals and antibiotics. Meanwhile, Zn2+ promote bacterial virulence by regulating quorum sensing, secretion and metal homeostasis systems, as well as oxidative stress response and virulence factor expression. Additionally, it highlights the potential of targeting Zn homeostasis as a strategy to combat environmental antibiotic resistance. Collectively, these findings provide key insights into the mechanisms by which Zn2+ regulate bacterial antibiotic resistance and pathogenicity, offering valuable guidance for developing strategies to mitigate the global threat of antibiotic resistance.

In order to investigate the prevalence of duck Tembusu virus (DTMUV) in several regions of China, this study conducted an epidemiological survey on 2674 avian throat swab samples (including chickens, ducks, geese, and pigeons) collected from seven provincial-level administrative regions in China in 2024. Following RT-qPCR testing, 198 positive samples were identified, demonstrating an overall positivity rate of 7.40% (198/2674) across the seven provinces included in the study. Subsequent virus isolation using BHK-21 cells led to successful isolation in 17 cases. Additionally, genetic evolution analysis of the partial NS5 gene was carried out on these 17 isolates through RT-PCR amplification and sequencing. The data analysis indicated that Guangdong Province had the highest positive detection rate, reaching 22.40% (86/384), followed by Henan at 12.24% (47/384). Among infected hosts, geese were primarily affected by DTMUV, with a positivity rate of 40.76% (97/238). The prevailing subgroup of DTMUV in circulation in China is subgroup 3.2. Farmer’s markets, wholesale markets, slaughterhouses, and poultry farms all showed evidence of DTMUV presence, indicating widespread contamination across diverse locations. This study examines the distribution, genetics, and phylogenetic features of DTMUV in China, which will enhance our comprehension of the epidemiological landscape of DTMUV in China.

Streptococcus suis is a significant zoonotic agent affecting both human and pig health and poses a substantial public health concern. The pathogenicity of S. suis is intricately linked to its ability to form biofilms and express virulence factors, which are regulated by the LuxS/AI-2 quorum sensing (QS) system. Herein, we uncover a novel therapeutic avenue by demonstrating that 5-fluorouracil (5-FU), an FDA-approved anti-cancer agent, effectively mitigates biofilm formation and attenuates the virulence of S. suis. Mechanistically, we observe a significant reduction in capsular polysaccharide and extracellular polysaccharide production upon 5-FU treatment, elucidating a potential mechanism for biofilm weakening. Additionally, 5-FU down-regulates virulence traits, diminishing S. suis's ability to adhere to host cells and evade phagocytosis. Crucially, our study identifies the thymidylate synthase regulatory gene thyA as a key mediator of 5-FU's effects on the LuxS/AI-2 QS system. Virtual molecular docking and gene knockout experiments provide compelling evidence that 5-FU modulates the LuxS/AI-2 QS system by targeting thyA. In vivo experiments further validate the therapeutic potential of 5-FU, showcasing a significant reduction in bacterial load and mitigation of tissue damage in a mouse model. In conclusion, our investigation unveils 5-FU as a potent disruptor of S. suis's biofilm formation and virulence, offering a promising avenue for the control of this devastating pathogen.

In bacteria, the glycosyltransferases play important roles in bacterial fitness and virulence. A prior transposon screen implicated glycosyltransferase Gtf-2 in the regulation of S. suis biofilm formation, but the biological function of Gtf-2 and how biofilm is modulated by Gtf-2 remains largely unclear. Here, we characterized the major components of S. suis biofilm matrix and further elucidated the its regulatory role in biofilm formation, which involved the regulation of S. suis extracellular matrix, c-di-AMP, cell surface properties, and bacterial energy metabolism. Additionally, we also revealed that Gtf-2 regulates the content and composition of capsular polysaccharide. Finally, the regulatory role of Gtf-2 in the virulence of S. suis was elucidated based on in vitro and in vivo infection models, and the loss of Gtf-2 function weakened the virulence of S. suis.

Conventional antibiotics exhibit limited ability to penetrate host cell membranes, making intracellular bacterial infections difficult to eradicate completely. As naturally derived nanoscale membrane structures, bacterial extracellular vesicles (EVs) possess excellent biocompatibility and intrinsic transmembrane transport capability, thereby demonstrating unique advantages for in vivo drug delivery. The present study investigated the feasibility of using EVs derived from the avirulent Streptococcus suis T15 as novel carriers for ciprofloxacin delivery. We also comprehensively evaluated the biosafety and anti-infective efficacy of this nanodrug delivery system in vitro and in vivo. Cytotoxicity assays, live/dead cell staining, and hemolysis analyses demonstrated that T15-derived EVs at concentrations below 50 μg/mL did not cause significant cellular damage or hemolysis. Serum biochemical analyses in mice further confirmed the absence of obvious organ toxicity, indicating favorable biosafety within the tested concentration range. Ciprofloxacin was successfully loaded into EVs using a combination of ultrasonication and electroporation, achieving a drug concentration of 438.6 μg/mL and a loading efficiency of 10.96%. The ciprofloxacin-loaded EVs (EV-CIP) exhibited significantly greater antibacterial activity than free ciprofloxacin against both intracellular bacteria and fluoroquinolone-resistant strains exhibiting efflux pump activity. Evaluation in animal infection models showed that EV-CIP markedly reduced mortality in infected Galleria mellonella larvae. It also decreased bacterial burdens in multiple mouse organs and significantly alleviated histopathological damage. These results collectively suggest that EVs derived from the avirulent S. suis T15 were safe and effective within the tested concentration range and experimental conditions. The EV-based ciprofloxacin delivery system substantially enhanced the clearance of intracellular pathogens and fluoroquinolone efflux pump-positive bacteria, suggesting its potential application in the treatment of difficult-to-treat bacterial infections. This study provides a theoretical and experimental basis for the further development of novel EV-based anti-infective drug delivery strategies for livestock and poultry.

Prokaryotes and eukaryotes endogenously generate the gaseous molecule hydrogen sulfide (H2S), which has been identified as a novel signaling molecule. Bacterial H2S plays a protective role against reactive oxygen species and antibiotic-induced cellular damage. Endogenous H2S can be produced by the assimilation pathway of sulfate and thiosulfate in Escherichia coli. The transcription regulator LsrR influences various bacterial characteristics. The results of the present study revealed that avian pathogenic E. coli (APEC) lacking LsrR exhibited increased H2S production and enhanced tolerance to oxidative stress. Transcriptome sequencing revealed the upregulation of genes related to the sulfate assimilation pathway after the deletion of lsrR. Further investigation demonstrated that LsrR acts as a transcriptional repressor, binds directly to the promoter region of cysPUWAM, and interacts with both CysJ and CysN, thereby inhibiting exogenous sulfate assimilation and decreasing the oxidative stress resistance of APEC. Additionally, the absence of lsrR facilitated the survival of APEC94 in macrophage RAW264.7 cells. Our findings suggest that LsrR represses resistance to oxidative stress in APEC by interfering with the sulfate assimilation pathway and provide valuable insights into host-pathogen interactions.IMPORTANCEAvian pathogenic Escherichia coli (APEC) exhibits complex serotypes and widespread antibiotic resistance, placing a significant economic burden on the poultry industry. The LuxS/AI-2 quorum-sensing systems, which are closely associated with bacterial growth, biofilm formation, and virulence, play important regulatory roles in the virulence of E. coli (including avian pathogenic E. coli, serotype O78) by regulating the bacterial response to diverse antibiotics. The LuxS/AI-2 system is under the transcriptional control of the LsrR repressor. Despite this, the pathophysiological function of LsrR in pathogen-host interactions remains elusive. The results of the present study revealed that LsrR plays a crucial role in modulating various biological properties of APEC. Specifically, it inhibits sulfate transport, thereby reducing both the resistance of bacteria to oxidative stress and their survival within macrophages. In summary, LsrR is involved in the regulation of key processes during pathogen-host interactions. These findings provide promising prophylactic strategies for the prevention and control of APEC infections.

Streptococcus suis (S. suis) is a zoonotic pathogen capable of causing meningitis and other diseases. However, the molecular mechanisms underlying its ability to cross the blood brain barrier (BBB) and invade the central nervous system remain incompletely understood. In this study, non-targeted metabolomics was used to investigate the effects of S. suis type 2 strain HA9801 infection on the metabolic profile of human brain microvascular endothelial cells (hBMECs), and to examine associations between key metabolites and BBB permeability. The results showed that HA9801 infection induced changes in the metabolic profile of hBMECs, with significant enrichment of the histidine metabolism pathway. Notably, several histamine-related metabolites were altered. Changes in HDC and HNMT gene expression, together with alterations in histamine-related metabolites detected by non-targeted metabolomics, were consistent with changes in histamine-related metabolism. These observed metabolic alterations were accompanied by significant accumulation of endogenous histamine, which was accompanied by reduced expression of tight junction protein genes (TJP1, OCLN, and CLDN5) and increased BBB permeability. Moreover, elevated histamine levels were associated with increased invasion and translocation of S. suis across the BBB. This study suggests that S. suis impairs BBB integrity in association with alterations in the host histidine–histamine metabolic axis, which were accompanied by increased histamine levels, reduced expression of tight junction protein genes, and enhanced bacterial invasion and translocation. These findings identify histamine-associated signaling as a potential pathway for further investigation in S. suis-associated BBB dysfunction.

Bacterial biofilms represent a major driver of persistent infections in animals, productivity losses, and increased antibiotic use. The chronic inflammation and metabolic dysregulation induced by biofilms constitute major predisposing factors for nutritional and metabolic disorders in veterinary settings. Conventional antibiotic therapy is often limited by reduced efficacy and the emergence of resistance in biofilm eradication. Moreover, drug residues and associated metabolic toxicity pose additional risks to animal health and food safety. Plant extracts, characterized by multi-target modes of action, favourable biocompatibility, and metabolic regulatory potential, represent a sustainable strategy for addressing this challenge. This narrative review systematically examines the mechanisms by which plant-derived compounds modulate the formation and dispersal of pathogenic biofilms via direct and indirect pathways.

Streptococcus suis (S. suis) is an important zoonotic pathogen that often forms biofilm, leading to persistent clinical infections and exacerbation of antibiotic resistance. There is an urgent need to develop novel antibiofilm strategies. In this study, for the first time, lactate dehydrogenase (LDH) was targeted with the aim of reactivating the metabolic activity of bacteria embedded in biofilm using natural product molecules, thereby disrupting mature biofilm. Through virtual screening based on the TCMSP database, molecular docking, and molecular dynamics simulations, two potential molecules, ginkgolide B and daidzein were identified. The results showed that ginkgolide B significantly eradicated mature biofilm of S. suis at 160 µg/mL, whereas daidzein did not exhibit such an effect. Ginkgolide B treatment led to a marked accumulation of tricarboxylic acid (TCA) cycle intermediates (pyruvate, malate, fumarate, and isocitrate), a substantial downregulation of the pentose phosphate pathway product ribose-5-phosphate, and a global upregulation of NADH as well as various high energy phosphate compounds and amino acids. These findings suggest that ginkgolide B may interfere with TCA cycle, leading to reduced lactate fermentation, enhanced accumulation of TCA cycle-related metabolites, and broader metabolic changes in biofilm-associated S. suis. This metabolic disturbance may contribute to the disruption of mature biofilm. This study validates the feasibility of a ‘metabolic activation’ strategy in eradicating mature biofilm of S. suis and provides ginkgolide B as a candidate molecule for the development of novel antibiofilm agents.

BACKGROUND:The emergence of drug-resistant Streptococcus suis (S. suis), driven primarily by antibiotic overuse in veterinary medicine and agriculture practices, threatens global public health. Antibiotic adjuvants that potentiate existing drugs offer a promising strategy to combat resistance. METHODS:We screened two small molecules targeting lactic dehydrogenase of S. suis. Hit compounds panaxadiol (PD) and vitamin D2 (VD2) were evaluated for metabolic modulation via aerobic respiration assays, NADH quantification, proton motive force (PMF) measurements, and metabonomics analysis. Aminoglycoside uptake and bactericidal activity were assessed in vitro and in vivo. All data are presented as mean ± SD from three independent experiments, and significance was determined by unpaired t tests (*P < 0.05, **P < 0.01, ***P < 0.001). RESULTS:PD and VD2 inhibited S. suis lactic dehydrogenase, suppressing anaerobic metabolism and redirecting pyruvate to the tricarboxylic acid cycle. This shift increased NADH production, amplified PMF, and enhanced uptake of PMF-dependent aminoglycosides. Both compounds synergized with aminoglycosides, significantly improving bactericidal efficacy against S. suis in vitro and in animal models. CONCLUSIONS:Targeting S. suis metabolic pathways with PD or VD2 restores aminoglycoside susceptibility, offering an adjuvant strategy to counter antibiotic resistance.

Streptococcus suis, a zoonotic pathogen, must adapt to the distinct nutritional environment of the host microhabitat during infection and the establishment of invasive disease, primarily by modulating its metabolic pathways. Metabolic plasticity endows S. suis with an enhanced capacity for environmental adaptation. Multidrug-resistant S. suis is increasingly prevalent due to the extensive use of antibiotics in swine production. In this study, an environment-dependent evolutionary model demonstrated that S. suis could modulate its metabolism in response to environmental changes, thereby altering its drug resistance and virulence. The central carbon flux regulated by pyruvate dehydrogenase (PDH) was identified as a pivotal node in balancing drug resistance and virulence in S. suis. Within the in vivo host environment, increased carbon flux through PDH enhances the production of capsular polysaccharide (CPS), thereby improving immune evasion. Conversely, in the antibiotic environment, reduced carbon flux through PDH downregulates the bacterial metabolic state, which diminishes the induction of toxic metabolites by antibiotics, thereby augmenting drug resistance. This concept provides a reasonable explanation for the puzzling phenomena observed with S. suis in clinical settings. For instance, antibiotic-resistant S. suis has a survival advantage in pig farms where antibiotics are frequently used but is less frequently associated with invasive infections. Furthermore, this study demonstrates that exogenous pyruvate can enhance the bactericidal effect of gentamicin against clinically multidrug-resistant S. suis, offering new insights and potential strategies for controlling clinical multidrug-resistant S. suis infections.

Streptococcus suis (S. suis) represents a significant bacterial pathogen, with its zoonotic transmission from infected or deceased pigs to humans posing a serious threat to public health. The type IV secretion system (T4SS), a critical virulence factor of S. suis, is tightly regulated by diverse environmental conditions. This study explores the influence of environmental variables, including temperature, incubation duration, monosaccharides, and metal ions, on the regulation of T4SS in S. suis and its associated pathogenicity. Results revealed that T4SS expression peaked during the stabilization phase at 37 degrees C, with galactose markedly enhancing T4SS expression relative to glucose. Zinc ions specifically enhanced the expression of the T4SS effector SspA among various metal ions. Moreover, zinc exposure significantly augmented both T4SS and virulence gene expression capabilities in S. suis. Zinc-treated S. suis exhibited enhanced adhesion, invasion, and colonization capacity in Hep-2 cells, Raw264.7 cells, and mouse models. These findings provide a deeper comprehension of the environmental modulation of T4SS in S. suis, paving the way for advanced studies into its mechanisms of pathogenicity.

The global rise in multidrug-resistant bacteria has significantly undermined the efficacy of traditional antibiotics. Multidrug-resistant Streptococcus suis (S. suis), a pathogen capable of infecting pigs and humans, has been identified as a critical threat, causing severe meningitis and rapid mortality. In response, researchers have increasingly focused on herbal compounds as non-traditional antimicrobial agents, which can inhibit bacterial growth while minimizing the risk of resistance development. This study investigates the mechanism through which andrographolide (AP) restores the susceptibility of S. suis to aminoglycoside antibiotics. The intracellular ΔpH in S. suis was assessed using the 2’,7’ -bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCCF-AM) probe to evaluate alterations in the proton motive force (PMF) following treatment with AP. Non-targeted metabolomics was employed to confirm changes in the metabolic profile of S. suis upon exposure to AP. Finally, an in vivo infection model was utilized to evaluate the therapeutic efficacy of AP in combination with antibiotics. Extensive in vitro experiments demonstrated that AP significantly enhances the activity of aminoglycoside antibiotics against diverse pathogens, including S. suis. Further studies revealed that bacterial death results from AP-mediated upregulation of the S. suis PMF, which enhances cellular uptake of tobramycin (TOB). Moreover, AP significantly upregulated pyruvate metabolism in S. suis, accelerated the tricarboxylic acid (TCA) cycle, and increased nicotinamide adenine dinucleotide (NADH) production. This metabolic shift further augmented the PMF. Combining AP with aminoglycoside antibiotics significantly reduced bacterial load and organ lesions in various organs in mice. AP holds promise as an adjuvant to aminoglycoside antibiotics for combating S. suis-induced infections, offering a theoretical foundation for clinical applications.

Streptococcus suis, a zoonotic pathogen, is commonly found as a commensal bacterium in the respiratory tracts of pigs. Under specific conditions, it becomes invasive and enters the blood, causing severe systemic infections. For S. suis, effective acquisition of carbon sources in different host niches is necessary for its survival. However, as of now, our understanding of the metabolism of S. suis within the host is highly restricted. Pyruvate formate lyase (PFL) plays a crucial role in bacterial survival of in glucose-limited and hypoxic host tissues. Here, we investigated the physiological and metabolic functions of PFL PflB in S. suis and elucidated its pivotal role in regulating virulence within the mucosal and blood niches. We demonstrate that PflB is a key enzyme for S. suis to support mixed-acid fermentation under glucose-limited and hypoxic conditions. Additionally, PflB is involved in regulating S. suis morphology and stress tolerance, and its regulation of capsular polysaccharide content depends on dynamic carbon availability. We also found that PflB is associated with the capacity of S. suis to cause bacteremia and persist in the upper respiratory tract to induce persistent infection. Our results provide highly persuasive evidence for the relationship between metabolic regulation and the virulence of S. suis.

The blood-brain barrier is a physiological protective barrier around blood vessels in the brain. It prevents most bacteria and harmful substances from entering the brain through the blood. However, when bacterial meningitis occurs, bacteria enter the brain either from the circulation or by direct invasion from neighbouring structures, causing an inflammatory response that in severe cases may lead to death. High morbidity and mortality are prominent features of the disease. Many pathogenic bacteria can break through the blood-brain barrier and cause meningitis, such as Streptococcus pneumoniae, Group B Streptococcus, Streptococcus suis, Neisseria meningitidis, meningitis-associated Escherichia coli, etc. This article reviews the mechanisms by which these bacteria cross the blood-brain barrier when causing meningitis and the interactions between bacteria and host cells to help pathogens invade the brain. Clarifying the mechanism by which pathogens cross the blood-brain barrier can provide new ideas for developing effective treatments for bacterial meningitis.

Escherichia coli (E. coli) O157:H7 is a major foodborne pathogen and a critical global food safety concern. Bacteriophage (phage) therapy offers a promising, highly specific biological alternative to antibiotic treatment. However, the clinical application of phage therapy is frequently limited by the rapid emergence of bacterial resistance. In this study, we examined the interaction between E. coli O157:H7 strain EDL933 and two T4-like phages, assessing the adaptive costs incurred by host strains in developing phage resistance. Our results indicate that phage PSD2001 utilizes capsular polysaccharide and lipopolysaccharides as adsorption receptors, while phage PNJ212 targets outer membrane protein C (OmpC) as its adsorption receptor. Notably, both phage employ gp37-like protein as receptor-binding proteins, highlighting the diversity of receptors on EDL933 and the complexity of phage-host recognition mechanisms. Furthermore, this study identified the adaptive costs of phage resistance, including antibiotic susceptibility, biofilm formation ability, survival, and colonization abilities, in the environment. These findings deepen our understanding of phage-host interactions and offer valuable insights for the application of phage therapy.IMPORTANCEPhage therapy offers an innovative strategy to combat antibiotic-resistant bacterial infections. To address the challenge of phage-resistant strains, we can adopt two strategies: using phage cocktails targeting multiple bacterial receptors to delay resistance development; and implementing a 'phage shift' treatment strategy that exploits the adaptive trade-offs of phage-resistant bacteria. Our research provides insights into the phage receptor recognition mechanisms in Escherichia coli O157:H7, a major foodborne pathogen. We identified key target receptors, including bacterial capsular polysaccharide, lipopolysaccharides, and OmpC, and found that the receptor-binding strategies of these phages resemble those of the T4 phage tail fiber protein gp37. Additionally, we revealed the adaptive costs associated with bacterial resistance to phage, which can inform strategies to enhance phage therapy efficacy. In summary, our findings provide a theoretical foundation for the prevention and control of clinical E. coli O157:H7 strains.

This study presents a synergistic bactericidal strategy combining engineered phage endolysin LYSMP-HPP with the plant-derived agent berberine hydrochloride (Bh) for controlling Streptococcus suis in foods and clinical settings. LYSMP-HPP, modified with a C-terminal hydrophobic short peptide (HPP), exhibits enhanced stability under food processing conditions (pH 5-7, heat, metal ions) while maintaining broad-spectrum bacteriolytic activity. In combination, LYSMP-HPP and Bh showed a strong synergistic effect on S. suis, reducing the minimum inhibitory concentration (MIC) of Bh to 1/8 compared to its use alone. LYSMP-HPP was shown to target specifically the hydrolysis of the cell wall peptidoglycan, while Bh disrupts membrane integrity, inhibits virulence genes expression and damages bacterial DNA, collectively leading to cellular collapse. Moreover, the combined treatment significantly downregulated genes encoding virulence factors and biofilm exopolysaccharides, as well as enhanced biofilm clearance and formation on porcine skin. In addition, bacterial load on pork surface was reduced by 4-5 Log10 CFU/g without affecting sensory quality. Safety assessments showed a 5 % decrease in the hemolysis rate and an 85 % increase in cell viability. In vivo experiments further revealed reduced bacterial load and damage in tissues. The strategy proposed herein is an efficient and safe solution for bio-preservation and a multi-target therapeutic option against resistant infections. Future work will focus on optimizing its scalability for industrial application.

The comprehensive antibiotic resistance of pathogens signifies the oneset of the “post-antibiotic era”, and the myriad treatment challenges posed by “superbugs” have emerged as the primary threat to human health. Recent studies indicate that bacterial resistance and tolerance development are mediated at the metabolic level by various signalling networks (e.g., quorum sensing systems, second messenger systems, and two-component systems), resulting in metabolic rearrangements and alterations in bacterial community behaviour. This review focuses on current research, highlighting the intrinsic link between signalling and metabolic networks in bacterial resistance and tolerance.

Streptococcus suis (S. suis) is a significant zoonotic pathogen. Owing to the widespread use of antibiotics in agriculture and farming, multidrug-resistant S. suis is proliferating, posing severe public health concern. The AI-2 quorum sensing (QS) system is a ubiquitous intercellular communication mechanism in both Gram-positive and Gram-negative bacteria, including S. suis, enabling it to coordinate fundamental life processes, adapt to environmental changes, develop antibiotic tolerance, and enhance virulence. In this study, SKQ1 demonstrated potent bacteriostatic and bactericidal activity against S. suis, with a lower propensity for resistance development. Mechanistic analyses indicate that this effect is likely achieved by compromising the integrity and functionality of the cytoplasmic membrane. Additionally, sub-inhibitory concentrations of SKQ1 significantly inhibited biofilm formation and reduced the virulence of S. suis. Untargeted metabolomics revealed that this effect may be mediated through disruption of the AI-2 QS system associated with methionine metabolism. Further investigations demonstrated that SKQ1 reduced the production of AI-2 signaling molecules, thereby diminishing biofilm formation and virulence. Owing to its antimicrobial activity and interference with the AI-2 QS system, SKQ1 exhibited robust therapeutic efficacy against diverse models of S. suis infection, including human isolates, multidrug-resistant strains, and highly virulent strains. This study offers novel insights into antibiotic strategies for managing porcine streptococcal infections and addressing the drug resistance crisis in S. suis.